St. John’s wort is a widely consumed herbal preparation which has been claimed to have a number of medicinal properties. It contains a number of known lipid signalling mediators, including chlorogenic acid, hypericin, hyperforin, and I3,II8-biapigenin. Hyperforin exhibits two activities which may alter the action of other concurrent medications. It inhibits the activity of several CYP450 enzymes, with CYP2D6 being the most sensitive with an IC50 of about 10 μg/ml. Hyperforin is also a ligand for the steroid X receptor (SXR). Since one activity of this receptor is the induction of CYP450 expression, the exact nature of hyperforin’s drug-drug interactions must be evaluated on a case-by-case basis. However, these interactions certainly complicate its use as a human therapeutic.
